ZX-636 Front End to 1976 KZ900-A4 Conversion: By Old Man Rock
I have rode bikes nearly all my life (first bike at 9 years old, I’m 49 now); I have repaired bikes to some form or another but haven’t really modified (Street Machine) a bike to this extent. So as others in the forum have been so gracious to provide their tips, experiences and expertise, I present this tutorial. I’m sure there would have been better ways to accomplish but this is what I did and I’m pretty excited about the results. So use as you wish, some of this may be helpful, some not or all of the following.
The tutorial was written so as to help other newbies such as myself in retro fitting/building the following; A Nice looking KZ900 with newer technologies incorporated.
NOTE: The first thing I highly recommend is Search, Review, Read and ask questions for EVERY forum posting on the subject matter at hand. If you don’t you wont succeed or at least you will put something together that for the most part my work but look like crap or worst case scenario won’t be optimum in operations, especially regarding safety.
Ok, here we go… Oh By the way, Buy the service manual!
The love of my life, a 1976 KZ900-A4:
Obviously the first thing to do is strip her down. All cabling was taped and marked. Only thing left was front and rear end.
As this tutorial is for the front end conversion I started by first removing the KZ900 front end down to the lower triple tree. As can be reviewed in the two images, I had a problem where the steering stem shafts are different sizes…DOH!
Obviously this translated into different size outer races pressed into the frame steering stem tube, CRAP!
KZ900 ZX636
Well then, no use in panicking for the only solution I had was to remove the KZ900 steering stem and press it into the ZX636 lower triple tree. Seemed easy enough but I had no idea what I was getting into for I was determined… LOL!
First step, removing the KZ900 steering stem from the triple tree. NOTE: This was the easy part!
As can be reviewed in the first image, we have a weld on the bottom of the steering stem to triple tree. The image on the right shows where I had to grind down ~ ¼” and tap out.
NOTE: The KZ900 steering stem taps from the bottom of the triple tree up though the top of the tree.
NOTE: Grind just until you see the steering stem tube, I unfortunately had ground down a little too far where welding a seam in the ZX636 triple tree later on was a bitch.
NOTE: I left the lower tapered bearing in place for correct height to top tree.
Now onto the removal of the ZX steering stem from the lower triple tree. I tried everything possible with heat and a 6 ton press. I searched for an answer and came up with nada, and even posted a question on the forum, still no answer for which way did this stem press out…
Now the answer, the ZX6R/636 steering stem presses down through the triple tree.
As can be reviewed below, the tree & stem bottom is notched and different in size where it can only go one way.
As written, even with heat and a press I couldn’t get this damn thing out so onto my local dealership and for $5, I had two pieces in my hand.
NOTE: Become friendly with your local techs!
Lucky for me, I have a metal manufacturer we have used in business for the last 8 years so I got a freebie on the triple tree sleeve.
Basically 37.5mm in height, 36mm in width where the whole opening is the same as the KZ900 steering stem.
NOTE: Remember where I told you to be careful, where this is what I was speaking of. The far right image shows the tack weld of the stem to sleeve. To get it down enough I had the top of the tree milled down ~ 1/8” and still had a hell of time getting a weld in there so be careful.
Lower triple tree with KZ900 steering stem complete!
As can be reviewed, in leaving the lower bearing, the height to the top triple tree came out dead on the money…. Sweet!
Front fork rotation:
With the increase in crease in fork tube size, the fork travel distance would hit the tank. Obviously this would not be good for the tank paint not to mention possible tube damage and for what I paid for these ZX636 forks I would not be a happy camper. Fortunately in my case, the previous owner had broken off the stop on the frame so I need to fabricate one anyways.
With new tank rubber dampers installed on the frame for exact measurements, place the tank into position and measure for travel.
With ¼” foam taped to the tank, rotate left and right to where the forks just touch the foam and measure… ~ 1 1/8” spacer is what I required. I used ¼” flat steel, 1 1/8” x 2.5” and tacked onto the frame. Rechecked the rotation, weld and grind a little and WHOLA!
Now this is where it really gets interesting, this front end is designed for clamp on steering bars. I’m 49 years old and there was no way in hell after what I’m going through on this project do I want to go for a ride and get a sore back. With that said, I needed risers, now how the hell do I do that was the next question…
In studying researching the ZX636 top triple tree it was going to be a bitch for the top of the tree is not flat. Sure, I found replacement trees that would accomplish for $500…. Ouch!
Here’s what I came up with where risers alone would get the bars up over the top of the fork tubes but I was concerned with stress on the tree. So a ¼” steel plate cut into the same diamond shape design of the tree would lock it into place, add surface support and rise the bars the needed distance.
NOTE: This was a bitch but worth it…
The risers I chose are polished aluminum riser ($60) for oversized handlebars (1 1/8”). I like the look of the thicker bars and due to new technology, less arm fatigue when riding. I also realized that until I updated to the larger bars I would require all new controls and throttle assemblies, all of which I just am not ready to do quite yet.
With this in mind, I needed to find oversized bars at the center clamp area that tapered down to 7/8” at the end of the bars. Renthal Street Low Bars had the answer ($80). I deliberated over chrome bars but decided to go with the black based on the color them of this bike and to throw some two tone effects into for the fork tubes are anodized orange/gold.
All in all, I now have the added support on the tree and in my eyes, a really nice look.
Hope you enjoyed,
Old Man Rock